JP2963903B2 - Plasma compensated cathode - Google Patents

Abstract

A plasma compensation cathode comprises a casing (1) accommodating coaxially with its outlet hole (2) a hollow holder (3) and a thermal emitter (4) with a central passage (5), a layer (10) of material chemically inert at high temperatures to the materials of the holder and emitter being interposed therebetween. The central passage (5) is blind at the side of admission of gas, and is communicated with the interior of the holder (3) by way of a through passage (8) made in the wall of the thermal emitter (4) so that its axis intersects the axis of passage (5), and longitudinal grooves (9) made in the side surface of the thermal emitter (4) at the location of the inlet holes of the through passage (8). The holder (3) is embraced by heater (6) having a support ring (7) positioned in its midportion and secured in an insulation sleeve (18) separating the heater (6) from the coaxial heat screens (11) interconnected successively to define a sealed cavity (14) wherethrough the interior of the holder (3) communicates with the gas feeding pipe (13) secured in the casing (1) through the support insulator (17). Interposed between mechanical filters (16) and between holder (3) and pipe (13) is a getter (15). <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to glowing compensating cathodes, and more particularly to plasma compensating cathodes.

[0002]

2. Description of the Related Art A casing, a cylindrical insert fixed to the inner surface of the casing and serving as a heat emitter,
Glowing cathodes are known which consist of a heater fixed to the outside of the casing and an orifice fixed to the end face of the casing and serving as an outlet opening for the cathode (see, for example, Schats, 1985 AJAA Transactions). MF "Heaterless Nission of Inert Gas Ion Thruster Hollow Cathode"). This configuration of the cathode requires a high power heater to heat the thermal emitter to a temperature that ensures sufficient thermionic emission to maintain a stable discharge.

[0003] Plasma-compensated cathodes are also known (for example, LA Artsimovich et al.
azrabotka stationarnogo p
razmennogo dvigatelaya IE
go ispytaniena iskusstven
nom sputnik Zemli Meetee
r "Kosmicheskie isledvan
is, 1974, tomxll, vyp, 3, 455-456). The compensating cathode has a casing with an outlet opening in one of its walls. The casing includes a heater surrounding a tubular holder for receiving a heat emitter having a central through passage, and a thermal screen located between the holder and the casing wall. A tube for supplying gas to the interior of the casing and to the passage of the heat emitter via the inlet part is connected to the tubular holder. This tube is fixed to the casing via an insulator.

[0004]

During operation of the compensating cathode, gas is supplied through the tubular holder to the passage of the heat emitter. The hot emitter heated to a high temperature ensures sufficient electron emission to maintain a stable electrical discharge between the inner surface of the heat emitter and the anode of the plasma source. After the device has been brought to a steady state of operation, the heater is de-energized. The compensating cathode continues to operate automatically, whereby a suitable temperature level is ensured by the energy released in the catholyte layer close to the ionic current resulting from the discharge due to the potential drop at the cathode. However, during operation, the discharge travels from the passage of the heat emitter into the interior of the tubular holder, evaporating the holder material and almost completely blocking the passage with the holder material. As a result, the heat release surface is reduced and the heat release current is reduced, thereby reducing the service life of the compensating cathode to only 10 hours. Furthermore, the direct connection of the holder of the heat emitter to the gas supply tube enhances the heat transfer from the emitter to the external structure. Thus, a noticeable catholyte potential drop occurs, guaranteeing the energy required to maintain the automatic operating state. The more pronounced potential drop also reduces the useful life of the thermal emitter due to intense ion bombardment. In addition, intimate contact between the heat radiating material and the holder at high operating temperatures involves active chemical interactions, such as, for example, boron penetration and the formation of metal borides.
And it causes brittleness or cracking of the holder material and the heat emitter, eventually causing irreversible deformation of the holder. This disadvantageous effect, in particular, limits the service life and reduces the total number of engagements of the compensating cathode. Also, the helical heater surrounding the tubular holder is of low rigidity, causing sagging or deformation of the coil causing possible contact of the coil with the short circuit of the holder or thermal screen and heater. This, in turn, results in little compensating cathode involvement and reduces service life. In addition, the working gas contains negligible contaminants such as oxygen and water and, at high operating temperatures, reacts with the material of the heat emitter, affecting the heat radiation properties of the material. With prolonged operation, tens or hundreds of hours, this disadvantage is more pronounced and the service life of the compensating cathode is reduced.

It is an object of the present invention to fix the discharge area in the passage of the heat emitter, prevent the heat emitter from chemically interacting with the holder material, so that the heat system has a minimum cathode potential drop and The present invention is to provide a plasma-compensated cathode configured to automatically maintain the preferred temperature of the heater, and to increase the rigidity of the heater and to facilitate extra cleaning of gas from impurities.

[0006]

The object of the present invention is achieved by employing the following configuration. That is, a casing coaxially housing a heat emitter having an outlet opening, a hollow holder and a central passage communicating with the interior of the holder, a heater surrounding the holder, and a wall between the heater and the casing wall. Heat screen arranged in the
A central passage of the heat emitter is closed on the gas inlet side, and a shaft of the through passage is provided in the plasma compensation cathode, which comprises a tube for supplying a gas to the inside of the holder fixed to the supporting insulator. Communicates with the interior of the holder via a through passage made in the wall of the heat emitter such that it crosses the axis of the central passage and the longitudinal groove made in the side of the heat emitter at the entrance opening of the passage. The interior of the holder, on the other hand, has a sealed cavity formed by the clearance between the coaxial thermal screens that are continuously connected by spacer rings and fixed to the gas supply pipes, and the inner surface of the holder and the holder material are hot. The space between the side of the heat emitter containing the layer of chemically inert material and the heat emitter, and in communication with the gas supply pipe, the heater comprises: A support ring fixed to an insulating sleeve separating the heater from the thermal screen at the center of the cavity, wherein the cavity employs a plasma-compensated cathode configuration containing a getter disposed between the mechanical filters. ing.

[0007]

Function: special passage for supplying gas, chemically inert material layer, coaxial heat screen system, support ring,
By using the plasma-compensated cathode of the thermal emitter of the present invention with an insulating sleeve, getter and mechanical filter, the service life can be substantially extended and the total activity of the cathode can be increased.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The plasma-compensating cathode comprises a casing 1 having an outlet opening 2 (FIG. 1). The casing comprises a heat emitter 4 with a hollow holder 3 and a central passage 5.
Are housed coaxially. The holder 3 is disposed coaxially with the outlet opening 2 inside the casing 1, and is surrounded by a helically shaped heater 6 having one end fixed to the casing and the other end fixed to the holder 3. Heater 6
Has a support ring 7 arranged in its central part and serving as an additional support point.

The central passage 5 of the heat emitter 4 is closed on the gas inlet side and has a passage 8 formed in the wall of the heat emitter 4.
Through FIG. 2, it communicates with the inside of the holder 3. The axis of this passage is provided on the side of the heat emitter 4 at the position of the axis of the central passage 5 and at the entrance opening of the through passage 8,
It extends perpendicular to the longitudinal groove 9. Layer 10 which is chemically inert with the material of holder 3 and heat emitter 4 at high temperature (FIG. 1)
Occupy the space between the inner surface of the holder 3 and the side surface of the heat emitter 4. A system of coaxial thermal screens 11 fixed to the gas supply pipe 13 to form a sealed cavity 14 and continuously connected via spacer rings 12 comprises:
It is located between the heater 6 and the wall of the casing 1. The interior of the holder 3 communicates with the gas supply pipe 13 through the cavity. In the space between the holder 3 and the tube 13, a getter 15 placed between mechanical filters 16 is incorporated. On the other hand, the tube 13 is fixed to the supporting insulator 17. The heater 6 is separated from the system of the thermal screen 11 by an insulating sleeve 18 to which the support ring 7 is fixed.

Next, the operation of the plasma compensation cathode of the present invention will be described. The gas flows along the tube 13 through the getter 15 and the mechanical filter 16 into the interior of the holder 3 and then through the grooves 9 and 8 into the central passage 5 of the heat emitter 4. The heater 6 acts to heat the thermal emitter 4 to a temperature that ensures sufficient electron emission to maintain a stable electrical discharge between the inner surface of the thermal emitter 4 and the anode (not shown) of the plasma source. I do. After the device has been brought to a steady state of operation, the heater 6 is de-energized and the compensating cathode operates automatically. Thereby, the required temperature level of the thermal emitter 4 is guaranteed by the energy resulting from the discharge.

When the central passage 5 on the gas inflow side is closed,
By changing the gas pressure and the shape of the passage 5, the electric discharge in the passage 5 can be stabilized. This is the heat emitter 4
To prevent the discharge fixation at the wall of the holder 3 which may cause the passage 5 of the holder 3 to be damaged or blocked, to easily maintain the initial heat release from the inner surface of the heat emitter 4, and to substantially extend the service life of the compensation cathode Increase.

By placing a layer 10 of a material which is chemically inert to the material of the holder and the heat emitter 4 between the inner surface of the holder 3 and the side of the heat emitter 4, the chemical interaction of the materials and The diffusion is eliminated, so that no irreversible deformation of the holder 3 or cracking of the holder 3 and the thermal emitter 4 occurs. As a result, the number of drives is substantially increased and the service life of the cathode is extended. The system of the coaxial thermal screen 11 forming the sealed cavity 14 together with the gas supply pipe 13 and the holder 3 comprises a heat emitter 4
From the holder 3 to the outer parts of the cathode structure, thereby reducing the cathode potential drop to the gas ionization potential level and substantially extending the service life of the compensating cathode.

The provision of the support ring 7 fixed to the insulating sleeve 18 increases the rigidity of the helical heater 6 so that even if the helical coil is substantially deformed by many thermal cycles, the helical heater 6 is Short circuit, ie
The engagement between the helical coil and the holder 3 or the screen 11 can be prevented. This also increases the number of drives and extends the useful life of the compensating cathode.

A getter located between the mechanical filters 16 immediately adjacent to the location where the gas enters the interior of the holder 3 is particularly finely chemically cleaned from a mixture of oxygen, water and the like, and A more stable heat emission characteristic of the heat emitter 4, which results in an extended service life of the compensation cathode, is ensured.

The present invention may be used to neutralize an ion beam in an accelerator having a closed electron drift and a long acceleration region, an accelerator having an anode layer and a narrow acceleration region, a plasma ion accelerator, and It can also be used to compensate for surface discharge.

[0016]

The present invention fixes the discharge area in the passage of the heat emitter and prevents the heat emitter from chemically interacting with the holder material, so that the heat system reduces the preferred temperature of the heat emitter with minimum cathode potential drop. It is possible to maintain the temperature automatically, further increase the rigidity of the heater, and easily clean the gas from impurities.

[Brief description of the drawings]

FIG. 1 is an overall view of a plasma compensation cathode of the present invention.

FIG. 2 is a sectional view taken along line II of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 2 Outlet opening 3 Holder 4 Heat emitter 5 Central passage 8 Through passage 9 Longitudinal groove 13 Gas supply pipe 14 Sealed cavity

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Gorbachev Yuri Mitrovanovich Koliningrad-Obier, Soviet Union. 7, D.7. 58 Be, Euel. Communisticeskaya (no address) (72) Inventor Ivanov Victor Alexevich Soviet Union of the Socialist Republic of the Soviet Union, Kaliningrad-Obier. 16, D. 75, Euel. Furunze (no address) (72) Inventor Kozbskiy Konstantin Nikola Evi ッ チ Kaliningrad-Obier, Commonwealth of the Soviet Socialist Republic. 24, Dee. 34, Euel. Frunze (no address) (72) Inventor Komalov Georgi Alexevich Soviet Union of Socialist Republics, Kaliningrad-Obier. 25. Dee. 27, Euel. Chardaeva (No address) (58) Field surveyed (Int.Cl. ⁶ , DB name) H05H 1/24 H05H 1/54

Claims (1)

(57) [Claims] 1. A casing coaxially containing a heat emitter having an outlet opening, a hollow holder and a central passage communicating with the interior of the holder, a heater surrounding the holder, the heater and the casing. In a plasma-compensating cathode composed of a heat screen arranged between the walls of the plasma emitter and a tube for supplying gas to the inside of the holder fixed to the supporting insulator, the central passage of the heat emitter is The wall of the heat emitter is closed on the inlet side and the axis of the through passage crosses the axis of the central passage and the longitudinal groove made on the side of the heat emitter at the entrance opening of the passage. The interior of the holder communicates with the interior of the holder via a through passage made in, while the interior of the holder is connected to a coaxial thermal screen that is continuously connected by spacer rings and fixed to the gas supply pipe. A space between the inner surface of the holder and the side of the heat emitter containing the layer of material that is chemically inert at high temperature to the holder material, and through the heat emitter. In communication with a gas supply pipe, the heater comprising a support ring fixed at its center to an insulating sleeve separating the heater from the thermal screen, the cavity being located between the mechanical filters. A plasma-compensated cathode containing a getter obtained.